Chairs generally aim for people seating or resting. In order to make limited living space be utilized more efficient in modern houses, many furniture producers have tried to improve conventional single-function furniture to become multifunctional to serve multiple purposes. Hence composite furniture is developed. It has features of simple assembly and transformation to provide multiple use states which probably also can be used at the same time. Therefore, one set of composite furniture can meet varying use requirements. For instance, Germany patent No. DE2327906 discloses a chair with a chair backrest that can be flipped for ninety degrees about a pivotal point to become tabletop. But the height of the tabletop cannot be adjusted after the chair backrest is flipped. Moreover, the flipping of the chair backrest relies on a single pivotal point which is easily to be damaged due to uneven applying forces or easily loosens off after used for a long period of time to result in changing the use states of the chair difficult.
Furthermore, Taiwan utility model No. M436398 also discloses a composite chair that provides multiple use states. It includes a rack and at least one carrying portion and one movable portion installed on the rack. The movable portion includes a movable deck, two coupling members and an adjustment member. Each of the coupling members has a fastening end hinged on the rack and a movable end hinged on the movable deck. The movable end can be turned about the fastening end in a rotary displacement. The adjustment member has two guiding tracks extended along the movable deck, a linkage bar with two ends held in the two guiding tracks and two movable arms respectively connected to the linkage bar and movable deck. When the linkage bar moves in the guiding tracks, the coupling members are coupled with the movable arms during the rotary displacement to drive the movable deck to move upwards or downwards against the carrying portion so as to change the chair to become different use states.
However, the movable deck of the aforesaid composite chair is coupled with the chair backrest through the coupling members and the position of the movable deck is controlled by the two guiding tracks of the adjustment member and the linkage bar. Such a structure cannot fix and support the movable deck securely. Users could inadvertently touch the movable deck to cause the linkage bar to slide along the two guiding tracks to change the height of the movable deck.